C # Design Pattern-Observer pattern (using delegates)

1. Concept

The Observer pattern (sometimes called the publish-subscribe subscribe> mode, model-view view> mode, source-listener listener> mode, or slave mode) is one of the software design patterns. In this mode, a target object manages all the observer objects that are dependent on it and proactively notifies when its own state changes. This is usually done by calling the methods provided by each observer. This pattern is often used to implement an event-handling system.

2. Roles

2.1 Abstract Theme (Subject): It saves references to all observer objects in a single aggregation, each subject can have any number of observers. Abstract topics provide an interface that allows you to add and remove observer objects.

2.2 Specific topics (ConcreteSubject): deposit the relevant state into a specific observer object, and give notice to all registered observers when changes are made to the internal state of the specific subject.

2.3 Abstract Observer (Observer): Define an interface for all specific observers and update yourself when you get a topic notification.

2.4 Specific Observer (CONCRETEOBSERVER): Implements the update interface required by the abstract observer role in order to reconcile its state with the subject state.

3. Implementation of the implementation of the mandate.

Simulated scene: The cat barks, the mouse runs, the master wakes up.

3.1 Isubject Abstract

     Public Delegate voidNotifyHandler ();
         Public Abstract classIsubject { Public EventNotifyHandler notifyevent; protected voidNotify () {if(Notifyevent! =NULL) notifyevent (); }         Public Virtual voidRun () {}}

3.2 Catsubject

    Public class Catsubject:isubject    {        publicoverridevoid  Run ()        {            Console.WriteLine ( " the cat called ... " );              This . Notify ();        }    }

3.3 Observer

   Public Abstract class Observer    {        protected  Observer (isubject sub)        {            + = Response        ;        }  Public Abstract void Response ();    }

3.4 Mouseobserver

   Public class Mouseobserver:observer    {        public  mouseobserver (isubject sub)            base(sub)        {        }         publicoverridevoid  Response ()        {            Console.WriteLine ( " the rat ran! ");        }    }

3.5 Masterobserver

 Public class Master2observer:observer    {        public master2observer (Isubject sub):Base(sub)        {                    }           Publicoverridevoid  Response ()        {            Console.WriteLine (" The master woke up .... " );        }    }

3.6 Calls

var New Catsubject (); var New Mouseobserver (sub); var New

3.7 Results

C # Design Pattern-Observer pattern (using delegates)